What is a Post & Crown?

What is a Post & Crown?

A post crown is a combination of a post (that extends down into the root canal of your tooth) and a dental crown. There is actually a third element called the 'core'. So sometimes, you will hear it referred to as a post and core, and crown- as generally this is how the components are split up when the dentist makes up your bill. There are always these three elements, it's just that sometimes the core is incorporated into the post (custom made) and at other times, it is built up on top of the post, in filling material. This happens after the post has been cemented. The latter is much more common nowadays. A post crown always requires a root canal to have been completed before it can be carried out. That's because the post extends deep down into the root canal of the tooth in order to get extra grip for the core. This is unlike a pin, which simply screws a couple of millimetres into the dentine of the tooth to help hold a filling.

When Would I Need a Post and Core?

A crown requires a solid core if it is to be successful and resist all the forces that will be placed on it for many years to come. If sufficient good tooth remains, a filling (either composite or amalgam) is all that is needed to provide a suitable core. However, if very little tooth remains and the core essentially consists of just one huge filling, it's going to be a lot weaker. The risk is that this will fracture and come off in the crown- a situation that dentists really hate to see. The reason is, it can't just be stuck on and any decent bit of tooth to help hold the core in place, has broken away- now, we have to rely solely on a post placed in the root canal to retain it. It makes a lot more sense to place the post initially- strengthening the whole structure and letting us make use of any good remaining tooth for the filling material to bond to. Sometimes the tooth will have already had a root canal, in which case, we can go straight ahead and place a post in the most suitable canal and build up a core for the new crown. If it hasn't, then we will need to do a root canal treatment first; the only other option is that we extract the tooth and think about a replacement for the missing tooth. There are two main circumstances in which posts are used:

• If you have had a root canal treatment and the remaining tooth is weak, a post will help to re-inforce this structure providing a more solid core for your crown. This is the most common use and avoids the situation that I described above; the crown breaking off with the core inside.

• If a tooth has fractured off at the gum level, so there is nothing but a root stub remaining. By sticking a post into the root canal, we can get extra grip to help hold the core for a crown. This is commonly seen and successfully carried out with anterior (front) teeth as they don't take the same pressures as your back teeth during chewing. A back tooth may require crown lengthening, in order to expose a bit more tooth for extra stability.There are two different basic types of post:

• Custom made. The lab make a post to match the impression of the inside of the canal . It will have a core included on top.

• Pre-fabricated. These come in different shapes and sizes and are placed directly by the dentist into the canal. The two most common materials used, are a carbon- fibre post and a stainless steel post. They can be parallel-sided, tapered and smooth or serrated. Threaded posts which are screwed in are no-longer used, as they set up a lot of stress in the root and make it prone to fracture. The other systems are really a matter of dentist preference.